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INTRODUCTION
In order to solve the seasonal shortage of water resources, Korea has artificially created reservoirs to secure water resources (Song et al. 2011). For most reservoirs in Korea, rapid eutrophication is underway due to the influx of pollutants from the summer rains (NIER 1999). Eutrophication of reservoirs causes phytoplankton blooming, which results in the hindrance to water purification process causing filtration problems, toxins, and unpleasant odors (Seo et al. 2003). Recently, various studies have been carried out to suppress phytoplankton blooming in Korea (Shin et al. 2014; Park and Jun 2016; Chung et al. 2017).
Among the Scenedesmaceae belonging to Chlorophyceae, the most taxa belong to genus Scenedesmus, which is floating, and it usually appears in the eutrophic ponds and lakes (Guiry and Guiry 2018). Scenedesmus was first named in Meyen (1829). Subsequently, Chodat (1926) divided genus Scenedesmus into several subgenus according to morphological features. The genus Scenedesmus has been described based on morphological features, as about 1,300 taxa (Hegewald and Silva 1988). The cell walls structure of subgenus Desmodesmus, which may be visible in light microscope as spines, short teeth, ribs or granulates (Hegewald et al. 1990). However, several studies have shown that genus Scenedesmus and subgenus Desmodesmus cannot be distinguished from one another only from their morphological characteristics (Trainor and Egan 1990; Trainor 1998). Thereafter, Scenedesmus and Desmodesmus separated as inferred from ITS-2 rDNA sequence comparisons (An et al. 1999). In recent years, many species of genus Scenedesmus have been transferred to genus Desmodesmus (Hegewald 2000; Guiry and Guiry 2018).
A total of 3,541 species of Chlorophyceae have been reported worldwide in AlgaeBase (Guiry and Guiry 2018), and 484 taxa have been reported in Korea (Lee and Kim 2015). A total of 562 taxa of Scenedesmaceae have been reported worldwide, of which 278 and 99 taxa were reported to be genera Scenedesmus and Desmodesmus, respectively (Guiry and Guiry 2018). A total of 149 taxa of Scenedesmaceae have been reported in Korea, of which 121 taxa were genus Scenedesmus (Lee and Kim 2015). Chlorophytes have been continuously added to Korean flora (Kim 2015, 2017; Jung et al. 2017; Kim and Kim 2017). Genus Scenedesmus was reported to 134 taxa since 2017, and the taxa of genus Desmodesmus have not yet been reported in Korea.
In this study, we collected phytoplanktons from various environments, such as small marshes, small ponds, reservoirs and brackish water. We aimed to add newly recorded species in Korean flora of phytoplankton.
MATERIALS AND METHODS
The collection of phytoplankton was conducted in various environments such as small marshes, small ponds, reservoir and brackish water in Gyeonggi-do, Jeollanam-do, Gyeongsangbuk- do and Jeju-do from March to November 2017 (Table1). Planktonic algae were collected by vertical and horizontal sampling using a plankton net with a diameter of 30 cm and a mesh size of 25 μm (Sournia 1978).
The samples were observed at 400-1000 magnification using light microscopes (Axio Imager A2, Carl Zeiss, Germany / Olympus BX41, Olympus, Japan). Photographs were taken using an AxioCam HRC camera (Carl Zeiss, Germany) and an Olympus UC-90 (Olympus, Japan).
The samples were separated into solid medium using a Pasteur pipette for the unialgal culture. When the colonies were grown in the solid medium, they were subsequently transferred to a liquid medium. Collected samples and unialgal-cultured samples were adapted to Bold’s basal media (Bold 1949) and incubated at 25℃ in a light / dark cycle of 16:8 with 40 μmol m-2 s-1 light (Stein 1973; Bold and Wynne 1978).
The taxonomic classification system was based on Algae- Base (Guiry and Guiry 2018), and morphological identification of the taxa was done by using Hirose et al. (1977), Komárek and Fott (1983), Hegewald et al. (1990) and John et al. (2011).
RESULTS AND DISCUSSION
Five species of the Scenedesmaceae were newly recorded in Korea. The newly recorded species found in this study were Scenedesmus nanus, S. praetervisus, Desmodesmus costato-granulatus, D. lunatus and D. spinulatus. We have provided morphological features and photomicrographs of the species (Figs. 1-5).
Family Scenedesmaceae
Genus ScenedesmusMeyen 1829
Coenobia are composed of 2 to 8 cells in 1 or 2 rows, with flat, straight and slightly curved. Cells are elongate, cylindrical, ovoid, ellipsoid to ovoid, with apices usually rounded. Cell walls are smooth, granular or warty. Chloroplast is parietal, with a single pyrenoid.
Scenedesmus nanus Chodat 1913 (Fig. 1)
Synonym:Scenedesmus carabusChodat 1926
Coenobia are composed of 2 to 4 cells, connected to the 1/2-2/3 of the cell length, and arranged to alternate slightly. The cells are oval in shape, and cell walls are smooth. A short spine appears on both ends of the outer cell, and a rare spine appears on the inner cell. The length of cell is 5.5-10.5 μm, and the width of cell is 2.5-4.5 μm.
Ecology: This species is rarely found in many ponds and reservoirs (Komárek and Fott 1983). We collected it from brackish water on the southern coast of Korea.
Distribution: Iraq (Maulood et al. 2013), China (Liu and Hu 2012).
Site of collection: 784-1, Haechang-ri, Anyang-myeon, Jangheung-gun, Jeollanam-do.
Date of collection: August 7, 2017.
Specimen Locality: ACKU2017IR09
Scenedesmus praetervisusChodat 1926 (Fig. 2)
Synonym:Scenedesmus armatus var. ecornis f. elegans Hortobágyi 1943
Scenedesmus armatus var. spinuliferum West and West 1901
Scenedesmus brasiliensis var. quadrangularis (Corda) Borge 1936
Scenedesmus brasiliensis var. spinuliferum Fott and Komárek 1960
Scenedesmus cieszynicus Sosnowska 1956
Coenobia are composed of 2 to 4 cells, linear or slightly alternating, and sometimes gently curved. The cells are oval to almost cylindrical, sometimes slightly asymmetrical or ovate and poles are rounded, obtusely conical to rounded- polygon. One short spine is straight or slightly oblique to the long cell axis, and the other two spines appear parallel to the outer long axis. Ribs show entire or interrupted on the cell sides, sometimes slightly toothed. The length of cell is 12.8-13.1 μm, and the width of cell is 5 μm. The length of spines is 4-7 μm.
Ecology: This species is planktonic and generally found in ponds and lakes. Most occur in the temperate regions and rarely in the tropical regions (Komárek and Fott 1983). We collected it from brackish water on the East coast.
Distribution: Netherlands (Veen et al. 2015), China (Liu and Hu 2012).
Site of collection: 163-49, Bugu-ri, Buk-myeon, Uljin-gun, Gyeongsangbuk-do.
Date of collection: May 31, 2017.
Specimen Locality: ACKU2017NR08
Family Scenedesmaceae
Genus Desmodesmus (Chodat) An, Friedl and Hegewald 1999
Coenobia are composed of 2 to 8 cells in one row, with flat, straight and slightly curved. Cells are elongate, cylindrical, ovoid, ellipsoid to ovoid, with apices rounded, truncate capitate, or narrowing to an obtuse point and always bearing long spines or teeth. Cell walls are smooth granular, spiny or toothed, with nipple-like projections or ribs often present in various combinations. Chloroplast is parietal, with a single pyrenoid.
Desmodesmus costato-granulatus (Skuja) Hegewald 2000 (Fig. 3)
Synonym:Scenedesmus costato-granulatus Skuja 1948
Coenobia are composed of 2 to 4 cells, with linear cells connected to three quarters of the cell length, completely disintegrating in the cultures. Cells are oblong ellipsoidal- oval, and conical-rounded at the poles, convex on the outside. Along the sides of the cell are some irregular rows of differently sized, colorless to dark, often merging into an incomplete. Between these ribs, granules of rib-like structure are scattered individuals. The length of cell is 4-4.7 μm, and the width of cell is 2.3-3 μm.
Ecology: This species is found in slowly flowing reaches of rivers, ponds and lakes (John et al. 2011). We collected this species from a small pond in hill.
Distribution: Netherlands (Veen et al. 2015).
Site of collection: Dongbaekdongsan, Seonheul-ri, Jocheoneup, Jeju-si, Jeju-do, Republic of Korea.
Date of collection: May 20, 2017.
Specimen Locality: ACKU2017NR06
Desmodesmus lunatus (West and West) Hegewald 2000 (Fig. 4)
Synonym:Scenedesmus denticulatus var. lunatus West and West 1895
Scenedesmus lunatus (West and West) Chodat 1926
Coenobia are composed of 2 to 8 cells, approximately 1/3 of the cells are linear or slightly alternating. The outer cells are semilunate-shaped with the poles bent outwards, and the inner cells are almost straight. At the end of the cell, 1-3 short teeth appear like spines. The length of cell is 9-9.6 μm, and the width of cell is 3-3.5 μm.
Ecology: This species is found mainly in the tropic areas and lives in small ponds with many aquatic plants (Komárek and Fott 1983). We collected this species from a small pond.
Distribution: China (Liu and Hu 2012), Netherlands (Veen et al. 2015).
Site of collection: Kyonggi Univ., 154-42, Gwanggyosan- ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, Republic of Korea.
Date of collection: November 7, 2017.
Specimen Locality: ACKU2017NR07
Desmodesmus spinulatus (Biswas) Hegewald 2000 (Fig. 5)
Synonym:Scenedesmus spinulatusBiswas 1934
Scenedesmus polydenticulatus Hortobágyi 1969
Coenobia are composed of 4 cells and slightly alternate (Komárek and Fott 1983, p. 869, fig. 10) or linear (Biswas 1934). Cells are oblong, oval-cylindrical with rounded poles on which 2-3 mighty, striking, different sized and divergence spines show. Some of these teeth on the outer cells are often oriented perpendicular to the long axis of the cell. The outer sides of the marginal cells covered with rows of very dense, fine, short, hair-like spines. The length of the spine is 2-5 μm, the cell is 10.9-11.3 μm, and the width of the cell is 4.2-5.4 μm.
Ecology: This species is rarely found in ponds (Komárek and Fott 1983). We collected this species from the static reservoir.
Distribution: India (Gupta 2012), China (Liu and Hu 2012), Russia (Medvedeva and Nikulina 2014).
Site of collection: Yonggok reservoir, Yonggok-ri, Jangdong- myeon, Jangheung-gun, Jeollanam-do.
Date of collection: August 7, 2017.
Specimen Locality: ACKU2017NR09
